A system has a plurality of integrated circuits mounted thereto as parts. In order for the system to normally operate, the integrated circuits included in the system should operate free of a fail. If a fall occurs even in one of the integrated circuits included in the system during operation, the system is sorted as a bad product.
A fall of a system may occur when noise is included in the system voltage supplied from a system controller to an integrated circuit, or jitter is included in a system clock. Therefore, an integrated circuit that exhibits system voltage noise or system clock jitter becomes unstable and a fail occurs in the integrated circuit, which may lead to a system fail. Jitter means a component that causes a change in the cycle and the duty ratio of the system clock.
Because system voltage noise or system clock jitter may be detected only after the integrated circuit is mounted to the system, a marked retardation in a system development project may result. Also, when the system fail has occurred, it is difficult to find where a failure has occurred in the mounted integrated circuit.